1. Field of the Invention
The present invention relates to a developing apparatus, a process cartridge, and a developer cartridge for performing development using a developing agent composed of charged particulates. Further, the present invention relates to an image forming apparatus provided with any one of them.
2. Description of Related Art
In a developing apparatus that performs development by electrostatically adhering toner serving as a developing agent composed of charged-particulates onto an electrostatic latent image, an unavoidable problem arises that the toner leaks from the developing apparatus. The toner having leaked from the developing apparatus pollutes the inside of an image forming apparatus body employing this developing apparatus. This has caused problems that poor printing occurs and that the hands and the clothes of an operator become dirty at the time of changing the developing apparatus.
In particular, in a developing apparatus of nonmagnetic single component development system in which a thin layer of toner is formed on a developing roller having the function of carrying and conveying toner by a layer thickness control blade so that development is performed by causing the layer to oppose an electrostatic latent image, toner leakage easily occurs from the vicinity of the rotating developing roller.
Thus, in the prior art, a developing agent leakage preventing member described below has been attached to a developing apparatus housing and a layer thickness control blade so that toner has been prevented from leaking from the vicinity of the developing roller. Specifically, for example, in a prior art disclosed in Japanese Patent Application Laid-Open No. 2001-134080, a side seal is attached to both end portions in the longitudinal directions of an opening in a housing of a developing apparatus so that toner is prevented from leaking from both end portions of the developing roller. Further, in the prior art described above, an upper seal is attached to a layer thickness control blade attaching portion in the developing apparatus housing, along the longitudinal direction, while a rib sponge and a rear surface side blade side seal are attached to a surface opposing the layer thickness control blade attaching portion in the layer thickness control blade. According to such configuration in the prior art described above, toner is prevented from leaking from a gap formed above the developing roller between the developing roller and the opening of the housing of the developing apparatus.
Nevertheless, in the prior art described above, side faces of the developing agent leakage preventing member for connecting an attaching face (housing attaching face) that attaches the developing agent leakage preventing member to the housing of the developing apparatus or an attaching face (layer thickness control member opposing face) that attaches the member to the layer thickness control blade to a surface opposing each attaching face is formed in a state orthogonal to the attaching face. Thus, when the developing agent leakage preventing member is pressed from the above by the developing roller or the layer thickness control blade, depending on the assembling state of the developing roller or the layer thickness control blade or alternatively the attaching state of the developing agent leakage preventing member, the direction becomes indefinite in which the side faces of the developing agent leakage preventing member is inclined and compressed. As a result, depending on the attaching accuracy of the developing agent leakage preventing member, problems can arise that a gap is generated in a portion in a member which should intrinsically oppose and contact closely with the developing agent leakage preventing member and that a passage for the developing agent is blocked. This causes leakage of the developing agent.